Hydraulic system utilizing flow dividers



April 19, 1949. L.. ZIMMERMANN HYDRAULIC SYSTEM UTILIZING FLOW DIVIDERS Filed Jan. 25, 1945 3 Sheets-Sheet 1 INVENTOR.

m, d m m M Z ma@ HTTUYPNEYS April 19, 1949. l.. ZIMMERMANN HYDRAULIC SYSTEM UTILIZING FLOW DIVIDERS Filed Jan. 25, 1945 s fshet's-sheet 2 rulli/lll? M w n a m d .c Maf. [w

'April 19, 1949. L. ZIMMERMANN 2,457,575

HYDRAULIC SYSTEM UTILIZING FLOW DIVIDERS 'Filed Jan. 25 1945 3 Sheets-Sheet 3.

@NMR Patented Apr. 19, 1949 N ITED .STATES A if..

T FFICE HYDRAULIC SYSTEM ernannte FLOW mvrnnies 19 Claims.

This invention relates to improvements in hydra'ulic systems utilizing 'new dividers.

Flow divi-ders are devices interposed between a source o'f ilui-d under pressure, such as a pump, and two or more huid-utilizing devices, such as hydraulic cylinders, or hydraulic' motors which are t'o be operated in synchron-ism. Without the use oi a flow divider the fluid-utilizing device which operates more freely Will operate more rap'- idiy than the other duid-utilizing device or devices, Infialring synchronism impossible. As examples oi flow' dividers,- reference is made to patenty to Methlin- 1,573,354, February 16, 1926, patent to Low 2,185,015, patent to Johnson 2,291,528-, and to the devices disclosedin applicants co-pendin'g application Serial Number 518,425 filed January 1944, now Patent No; 2,454,418.

Generally speaking, flow dividers may' con sist of two or more hydraulic pumps (or hydraulic motors)v the rotating elements of which are Inechanically connected together., said elements having a common admission conduit connected with a source of fluid under pressure and separate delivery conduits connected to` the respective fluid-utilizing devices. Since the elements of the now divider must rotate together the delivery of fluid to the fluid-utilizing `device is,` o'f course, correctly proportioned, irrespective of pressure difference in the 'divided conduits, (except for leakage in theV hydraulic elementsi.. If thev delivery of fluid from one'of the' outlets should be resisted, as when any mechanism operated thereby is jammed, the flow divider will act as' a pressure booster' and exert a greater' pressure upon the conduit leading to the' fluid-utilizing devlcewhich. is most difcult to operate. Thus, in a flow divider having tWo elements (and two outlets) when one of the' outlets is subjected to substantiallyv zero pressure. Whereas the other outlet is obstructed, due tol resistance against' thel operation of its fluid-utilizing device, the pressure on` the second line WillI be substantially double vthe onel of whichl may occasionally get out of order so that it Will need additional pressure for its operati-on. Thus, a oW divider is able' to deliver several streams of iluid in predetermined volume' proportions at ilierent pressures, some' 'of which may exceed the inlet pressure. The relationship' is that the sum of the pressures existing in the outlet lines of a now divider having any number of sections equals the inlet pressure times the number of sections.

This characteristic of flow dividers While having the above mentioned advantage has ther disvide means' for` use in hydraulic' systems en'iploying4 flow dividers for limiting the' pressure inoutlet line from the flow divider Without disturbing the predetermined tloW division'.4

Another object is to' provide such a device cludin'g means controlled byv the pressure 'in' any outlet from a flow divider, ir/hicli` means serves to bleed' the inlet line to the iloiv divider When'- ever the pressure in any outlet line thereii'orrl reaches' the desired r'naXinrui-n value.-

Another object is te provide such' pressure-limiting inea-ns in which there is a' single valve for bleeding the inlet line,` the'- effectivity off valve is controlled' by pilot valves which' arec'enh trolled by theA pressure in the respective outlet lines.

Another' object' is to' provide pressure-limiting' means in such a system` in which the linlet lineto" the flow' is throttled so that no bleeding iron` said line' is necessary.

Another obljec't is to provide pressureeliiniting'i means in such a system in which the inletv line te thefflow divider is throttled' so't`loe-A.'y no bleeding from saidv line is necessary, said' throttling means being controlled' by pilot valves' which arie oontrolled by the pressure in their respective outlet'- lines.

Another object is tc provideV such pressure-limiting means' making. use of' bfoth throttl'ing bleeding'.

Still another object is :to provide such pres-- sure limiting means ina-hing useA of both` throt# tling and bleeding, the pressure-limiting means being controlled by pilot valves which are controlled by the pressure in the respective outlet lines.

With the objects above indicated and other objects which will appear from the drawings and the following description, my invention consists in the construction and combination of elements hereinafter described and claimed.

Referringto the drawings:

Fig. 1 is a schematic illustration of a form of the device including two bleeder valves for bleeding the inlet line to a two-way ow divider under control of the pressure in their respective outlet lines from the ilow divider;

Fig. 2 is a view similar to Fig. 1 of a modification in which a single bleeder valve is controlled by pilot valves;

Fig. 3 illustrates another modification in which the inlet to the flow divider is th-rottled by valves controlled by pressure in the respective outlet lines;

Fig. 4 illustrates another modification showing a throttling valve in the inlet line controlled by pilot valves which are controlled by lthe pressure in the respective outlet lines;

Fig. 5 shows another modification in which pressure control is effected by valves which throttle the inlet line and bleed the inlet line beyond the throttle, said pressure control means being operated under the control of pressure in their respective lines; and

Fig. 6 illustrates another modiilcation in which lpressure cont-rol is effected by a single valve which throttles the inlet line and bleeds the inlet line beyond the throttle, said pressure control means being operated under the control of pilot valves which are under control of i-the pressure in the respective outlet lines.

. lReferring to Fig. 1, II indi-cates a sum-p containing a supply of fluid from which fluid may be drawn through conduit I2 by a, pump I3 of any desired construction. I4 indicates the delivery line from said pump which communicates with conduit I5 which is the inlet line for the flow divider IS of any desired construction. I'Ia and I'Ib are outlet conduits from the flow divider which supply fluid-utilizing means, such as hydraulic motors I8a and I8b. I 9a and Illb indicate lthe return -conduits from the hydraulic motors. 20 indicates generally a body which may contain the ilow divider as well as the bleeder valves to be presently described. It is however to be understood that the flow divider may be ia separate structure. The control valves may include cylindrical bores 2Ia and 2lb which house slidable cylindrical Valve pistons 22a and 2217 formed, as shown, with a portion of reduced diameters 22a and 22b. They are normally held in the position shown by means of spring-s 23a and 23h respectively which bear against adjustable abutments 24a and 24h respectively. The upper ends of the cylindrical bores are connected by passages 25a and 25h with the outlet lines I'Ia and Ilb respectively.

Near the center of the cylindrical bores are annular enlargements 26a and 2Gb which are connected through passages 21a and 2lb 4with the inlet line I5.

The cylindrical bores are also provided with annular enlargements 28a and 28h which are connected to each other by the passage 29 and are connected through return line 30 with the sump. The conduit 29 is shown as connected to the space -below the piston valves by passages 3Ia and 3Ib. These annular enlargements serve as valve ports and they, as well as other similar means, may on occasion be referred to as ports. In most cases a simple aperture in the wall of the cylinder bore would serve as 'well but, for manufacturing reasons, the use of annular enlargements is usually preferred.

The operation of this form of the invention is as follows:

The pump I3 delivers oil to the ilow divider I6 through the control and reversing valve I3a and conduits I4 and I5. The fluid is divided by the flow divider and delivered through conduits IIa and I'Ib to the fluid-utilizing devices such as the hydraulic motors I8a and I8b. After leaving said motors the iluid is returned through conduits I9a and ISb through control and reversing ing valve I3a and conduit I3a' tothe sump. The springs 23a and 23h have been adjusted to the maximum pressure desired in outlet conduits IIa and I'Ib. If, in the operation of the device, the pressure in one of the outlet lines as, for example, I'Ia, should exceed the desired maximum (due t-o an excessive load on motor I8a) the valve piston 22a will be moved downwardly against the bias of spring 23a suiliciently far to cause the reduced portion 22a of the piston valve to align with the annular enlargement or port 28a. This will permit fluid to escape from the inlet line I5 through passage 21a into the cylindrical bore, thence into the annular port 28a and through return conduit 30 to the sump. As the amount of fluid which the pump I3 can deliver is limited, the pressure in the inlet conduit I5 will drop; causing a corresponding drop in pressure in the out-let conduit Ila. When this 4pressure drop has reached the desired value, the spring 23a will move the piston valve upwardly and thus shut off the ow from the inlet line I5.

Passages 3Ia and 3Ib are provided merely for the purpose of permitting the escape of any oil which may have leaked by the valve pistons and accumulated in the spring housing space.

The other valve means operates in the same manner under the control of pressure in outlet line I1b.

It will be Seen that the construction described above will serve effectively tolimit the pressure in either outlet line to a valve determined by the setting of the valve springs 23a or 23h, without disturbing the accuracy of ow division.

The form of device shown in Fig. 2 is an improvement over that of Fig. 1 in that only one bleeder valve is needed. The bleeder valves of the form shown in Fig. 1 must each be suillciently large to bleed sufficient fluid from the system to keep the pressure in the system to a safe limit. In order to avoid providing one of these relatively large valves for each section of the ow divider, which would become expensive and bulky, particularly in a system including a flow divider having many sections, the form of Fig. 2 in which only one bleeder valve is needed, has been devised.

Referring to Fig. 2, the reference numerals I I, I2, I3, I3a, I3a', I4, I5, I6, I'Ia, I'Ib, Isa, I8b, I9a, and I9b refer to parts substantially identical with parts of the same number appearing in Fig. 1. The numeral 35 indicates generally a body which may contain the ow divider, the bleeder valve, and the pilot valves, to be presently described. This body is shown as provided with a cylindrical bore 35 containing a valve piston 31 normally pressed downwardly by a spring 38. It is formed with a reduced clearance portion 39 and preferably with a `strokelimiting protection 401. This valve bore is provided with an annular enlargement 4I which is 'connected through pasV sage 42 with the Ainlet line I5. Itis `also provided with an annular enlargement 43 which is connected through passage -44 with `a .return conduit 45. The passage 4B connects 'the space above the .piston with the return conduit -45 to permit the escape o-f any leakage oil. The space below the piston 'is connected .to the return conduit' #5 by means of a passage lll which contains a restriction 41a, therein.

Pilot valves for controtling the voperation of the valve means 3lv are shown` as consisting' ot cylindrical bores a 'and 5'Ilb` containing valve pistons 5Ia and 5ib formed with central reduced portions 52a and 52h and normally pressed upwardly to the position `shown by means of springs 53a and 53h, the bias of whichmay :be `adlusted by means of the threaded spring fabutments L54a and 5417.

The valve bores 50a` and 50h are formed with annular enlargements .55a and 55bwhich-are connected together and through conduit 56 with the inlet line I5. The valve bores 50a Aand 50h are also provided with annular enlargementsy 51d and 57h which are connected together and 'are connected through conduit v58 with the space below the main bleeder valve piston 3.1. The lspace above the pistons 5Ia and 5Ib `are connected with the outlet lines Ila and I'Ibl respectively by means of passages 59a and 5917. The spaces below the valve pistons are connected to each other by passage 45' Aand to the conduit 45 by passage 45".

The operation of the 'device of Fig.. 2 is as rol'- lows;

The parts are normally in the position. shown in which no bleeding from the inlet- .line .I5 can take place. If, however, the pressure in one .of the outlet lines. say the line `I la, should -riise above the desired value, the valve piston `51a will be moved downwardly `against the 'of spring 53a. When this occurs, fluid from inlet line I5 flows through passage 56 into the annular er-ilargemeut 57a into passage 58 under the bleeder vatlve piston 371, moving it upwardly until the reduced central portion 39 thereof alignsv with the annular port 43. This permits nuidto pass .from the inlet l-ine I5 through passage 42, the annular enlargement IlI, the port 43, passage 44, and return conduit 45, to the sump. This wi-l-l immediately cause the pressure in the inlet line I5 to 'drop and therefore cause a corresponding drop in the outlet line I'Ict. This permits the valve piston 5ta to rise under action of spring 53a shutting off the pressure to passage 58. The valve piston 35 will thereupon drop under action of spring 3 8.

During this time, iiuid under the piston will leak through the restriction 41a to the .return conduit 45. This fluid has come yfrom the inlet line I5 and not from linelIa so that the accuracy of flow division will not be affected.

The other pilot valve 5Ib will operate in the same manner under control 'of pressure the outlet line IIb. It will be seen thereforethat this. arrangement will serve to prevent excess pressure in either outlet line while. not -disturb'- ing the accuracy of `flow divisionand that this can be accomplished by -a single bleeder valve irrespective of the number of sectionsinthe new divider. Itis of cou-rse Anecessary to provide a pilot valve for each `section of the now divider but these valves may be made very small and inexpensive.

'The :forms oi the invention shown in Figs; 3 and' accomplish reduction of pressure in the inlet lines vand ltherefore in the outlet lines, by throttling the supply vvci' fluid to 'the inlet line rather than bleeding vor `bypassing -some of the fluid. This method is .preferable whenever the iiuid is supplied from Ian accumulator as it avoids discharging of the accumulator if one o'f the hydraulic motors is stalled by overloading for any considerable period of time. This form of device is also useful where the nuid is supplied to the flow divider from a pump having automatic means for Ain'aintaining a predetermined pressure. In that connection, I have in mind a variable volume positive displacement pump, the delivery volume of which is decreased automatically upon the. occurrence of increase in pressure.

If such a -pump were -used with the systems of Figs. 1 and 2 the pump would be automatically adi-usted to increased volume upon vthe opening of the .bleeder valve or valves :in an ei'lort to maintain the pressure. This would necessitate extremely large bleeder valvesand result in a waste of energy.

Referring to Fig. 3, the reference numerals I i, I2, I3, 13a, If3a', I4, I5, i6, I'Ia.,'I1b,I8a, I8b, I 9a, and -Ib refer to parts Vsubstantially identical with .parts of `the same number `appearing in Figs. 1 a-nd 2. I 3 represents an unloading valve of any known-or suitable construction. Such valves cause the pum-p to be connected to deliver to the Aaccumulator until pressure in the accumulator has reached the maximum desired value. Then it disconnects the pump from the line to the accumulator and connects the pump directly to the sump, as through line I3 so that the pump will circulate fluid against only a very low pressure, thereby saving power. In the meantime, the system will. be supplied from the accumulator. After the accumulator pressure has dropped to the lower pressure limit for which the unloading valve has been set, the unloading valve will again `connect', the pump to deliver liquid to the accumulator. r6I) indicates a hydraulic accumulator connected through 'conduit 6I with the conduit I4. Instead of the rel-lef valve I3 and the accumulator 6U, the pump I3 may, if desired, be of the type -having variable volume and means for controlling the volume inversely with the pressure in line I4 so that said pump will maintain a constant pressure in said `line I4'. 62 indicates generally a body which may contain both the .flow divider and the pressure control valves -to be presently described although the valves and ilow divider may, -of course, be arranged separately. Said body is shown provided with cylindrical bores 63a and 63h having `annular enlargements Ii4a 64b, 65a., 65h. Said bores contain valve pistons 66a `and 6619 each formed with a reduced central portion 61a. and 67h which are connected by conical portions Gla and vi'ib' with the full diameter portions at the left end of said valve pistons.

Springs 68a and 68h normally hold said valve pistons to the left, Yas shown. Said springs may be set to the desired value by varying the posi tion of. the adjustable spring abutments 69a and 69h. The annular enlargement 65a is connected with the conduit I4 :and the annular enlargement h isy connected with the conduit `I'5 which is `the inlet .line tor the flow divider. 'The annular enlargements 64a. and 64b are connected with each other and normally the enlargement Lfida `is Vconnected with the enlargement '55a and therefore with the conduit I4 whereas enlargementrli'b is normally connected with the enlargement 65h and therefore with the conduit I5, thus establishing connection from the conduit I4 to the conduit I5. Passages 10a and 10b serve to connectthe outlet lines I1a and I1b respectively with the spaces to the left of the pistons 66a and 66h, respectively. The spaces within which the springs 68a and 68D are housed are connected to each other by a passage 1I and a conduit 12 serves to drain any leakage collected in the spring space of either valve back to the sump.

The device of Fig. 3 operates as follows:

With the parts in the position shown, lluid will be delivered from the pump and/or accumulator to the ilow divider where it is divided and transmitted to the duid-utilizing devices such as the hydraulic motors I8a and I8b respectively. If now the pressure `in one of the outlet lines, say |1a, should exceed the desired amount, the pressure therein will be conducted through passage 10a to the space to the left ofvalve piston 66a, causing said piston to move to the right against the bias of spring 68a. When the conical portion of the piston 66a approaches the limit of the annular enlargement 64a, it serves to throttle the fluid thereby reducing the fluid delivered to the flow divider and consequently the pressure in the passage I which is the inlet line to the ow divider. Drop in the inlet pressure will result in a corresponding drop of the outlet pressure in line I1a. When this occurs, the piston 66a will move to the left but will maintain a position which will assure that the pressure in line I1a can never exceed the one for which the spring 68a is adjusted. The other valve piston 66h will operate in the same manner under control of pressure in the line |1b. It will be noted that the two throttling valves are arranged in series so that either one can control the flow.

Fig. 4 illustrates a form of the invention in which a single pressure throttling valve lis used, the ellectivity of which is controlled through pilot valves by the pressure inthe outlet lines of the flow divider.

Referring to Fig. 4,. the numerals II, I2, I3, |3a, I3a', I4, I5, I6, |1a, I1b, I8a, I8b, |9a, I9b, I3', I 3, 60, and 6I refer to parts substantially identical with parts of the same number appearing in Fig. 3. The numeral 15 indicates generally a body which may contain the flow divider as well as the pressure control valves although they may be arranged separately. 16 indicates a cylindrical bore therein provided with annular enlargements 11 and 18. In said bore is located a piston 19 having a reduced central portiony 80 which is connected by a conical portion 80- with the full diameter lower portion of the valve piston. Said piston is normally held in its lowest position by means of a spring 8|. The annular enlargement 11 is connected with the conduit I4 and is normally connected with the annular enlargement 18 which is connected to `passage I5 which serves as the inlet line for the flow divider.

The body is shown as also formed with cylindrical bores 82a and 82h formed with annular enlargements 83a and 83h connected with each other and annular enlargements 84a and 84h connected with each other. Said bores contain valve pistons 85a and 85h respectively, said pistons being formed with central reduced portions 86a and 86h respectively. The pistons are normally held in the upper position shown by means of springs 81a and 81h, the bias of which mayV be varied by adjustingl the adjustableI spring abutment plugs 98a' and 88h. 'Ihe upper portions of the pilot valve bores are connected with outlet lines I1a and I1b by means of passages 89a and 89h respectively. The annular enlargements 83a and 83h are connected through passage 90 with the conduit I5 and the annular enlargements 84a. and 84h are connected through conduit 9| with the space below the throttling valve piston 19. Said space is also connected through passage 92 having a restriction 92 with a return conduit 93 which is also connected to the space above the valve piston 19. Fluid accumulating below the pilot valve piston may escape through passages 94 and 93 to the sump.

`The operation of the device of Fig. 4 is as follows:

The conduit I4 is normally connected to the conduit I5. However, if the pressure in one of the outlet lines as, for example, outlet line I1a, should rise above the predetermined value the pilot valve piston 85a will be moved downwardly, admitting pressure from line I5 into passage 9|, causing Vthe throttling valve piston 19 to rise. As the conical portion thereof approaches the upperlimit of the annular enlargement 11, it causes the fluid to be throttled, resulting in a reduction in pressure in the line I5 which is the inlet to the flow divider, and a corresponding drop in pressure in the outlet line Ila. This permits the pilot valve piston a to rise, shutting off the supply of fluid to conduit 9|. The throttling valve piston 19 will thereupon drop under the action of spring 8| at a rate permitted by the restriction 92. In this construction, as in that of Fig. 2, the fluid which drains away at this time, and for that matter during the time while the bottom of valve piston 19 is under pressure, is obtained fromline I5 and the loss therefore does not interfere with the accuracy of flow division.

The action of the other pilot valve 85h is the same as described except that it occurs under control of the pressure in outlet line |1b.

The throttling methods of controlling the inlet pressure to the ilow divider and thereby the outlet pressure, as shown in Figs. 3 and 4, have a certain disadvantage. Thus, in case of a reversed motion of the hydraulic motors or other fluid-utilizing means due to their being overpowered by an external force applied thereto, the rising pressure in the outlet line will close the throttling valves (66a or 66h in Fig. 3, or 19 in Fig. 4), thus trapping the uid. This may result in damage to the driven mechanism or to the ow divider or cause bursting of conduits. This difiiculty does not exist where a bleeding valve is used, as in Figs. 1 and 2, lsince under these circumstances the lluid may escape to the sump. The systems shown in Figs. 5 and 6 avoid the disadvantage I have referred to and combine the advantages of the bypass or bleeder type with those of the throttling type.

Referring to Fig. 5, the numerals I2, I3, I3a, I3a, I4, I5, I6, Ila, |1b, I8a, ISb, I9a, |9b, I3', I3", 60, and 6I refer to parts substantially identical with parts of the same number appearing in Fig. 3. 95 indicates generally a body which may contain both the flow divider and the pressure control valves to be presently described although the valves and llow divider may, of course, be arranged separately. Said body is shown as provided with cylindrical bores 96a and 96h, the bore 96a having annular enlargements 91a, 98a, 99a, and I00a, and the bore 96h havlng annular enlargements 91h, 98h, 99h, and

i001). Said bores containk valve. pistons lilla` and IIlIb respectively. The valve piston IllIa is formed with reduced portions I02a, and I03a whereas the piston IIlIb is formed with reduced portions |0217 and I03b. The said reduced portions are preferablyv joined to their full-size terminal portions by the conical sections shown.

Springs I04a and Illb normally hold said valve pistons to the left, as shown. Said springs may be set to the desired value by varying the position of the adjustable spring abutments Illa and |0512. The annular enlargement 98a is normally connected With the annular enlargement 91a which is always connected to the annular enlar-gement Q'Ib which is normally connected to the annular enlargement 98h which is always in communication with conduit I5 which is the inlet conduit to the flow divider. It will be seen therefore that there is normally an open communication between the conduit I4 and the conduit I5. The annular enlargements 99a and 99D are always connected and the annular enlargement 99h is connected to the conduit I5 by a passage |06. The annular enlargements IIlUa and Illb are connected together and the enlargement Ia is connected with the return conduit |01 leading to the sump. The spring spaces to the right of the valve pistons are connected by a drain passage I 08 and are connected with the return conduit I'Il'I by a drain passage m9. The left ends of the valve piston bores are connected by conduits Illiay and IIIlb with the outlet lines IIa and IIb, respectively.

The device of Fig. 5 operates as follows:

With the parts in the position shown, fluid will be delivered from the pump and/or accumulator to the flow divider through conduits I 4, ports 98a, 91a, 9lb, and 98h through passage I5. The flow divider divides the flow which is transmitted to the fluid-utilizing devices I8a and I8b in predetermined proportions. If now the pressure in one of the lines, say I'Ia, should exceed the desired amount, the pressure therein will be conducted through passage IlIla to the space to the left of valve piston Ila, causing said valveto move to the right against the bias of spring Illa. When this occurs, the conical portion to the left of the reduced section IZa approaches the limit of the annular recess 91a. This serves to throttle the fluid which would otherwise pass freely from the conduit I4 to the conduit I5. In so doing, it reduces the pressure in the inlet line I5 to the flow divider which results in a corresponding drop of the outlet pressure in line I'I-a. If the valve piston IUI a should be moved still further, the conical portion to the right of the reduced section I03a of valve piston I0 I a, begins to align with the annular recess Ia, thus opening a passage from inlet line I through passage |06, annular recess 99D, annular'y recess 99a, annular recess IIlIIa, through return pipe I0'I to` the sump. This bleeding of the line I5 will permit reverse movement of the hydraulic motors I8a and IBb for reasons and under circumstances to be described presently. The bleeding off part of the valve does not begin to open until after the throttling part is entirely closed, so that at no time is there simultaneous throttling and bleeding. It depends upon the nature of the load on the hydraulic motors whether they pressure is controlled by the throtting part of the valve. or by the bleeding olf part of the valve. If for example the load is purely of the friction type, and this load exceeds the permissible value the hydraulic motors will merely stall,

and there is no danger of the hydraulic motors being reversed by their load and under this condition the pressure will be controlled entirely by the throttling part of the valve. However, if the external load is of such a nature that it is capable of overpowering and reversing the hydraulic motors, as for example in case of wind pressure acting upon the wing naps of an airplane, the throttling will give control of the pressure in the flow divider outlet lines only as long as the flaps are not reversed. Whenever the flaps meet with an excessive wind pressure such as may be caused by gusts of wind or by flying at too high a rate of speed, with the aps down, the pressure in the outlet lines is caused by the reversed motion of the hydraulic motor or cylinder and it is at this time that the valve is moved beyond the throttling position into the bleeding off position. This provides a very important safety factor. The valve parts may be so proportioned and the springs so set that the flaps will be moved to or held in their effective position only to an extent consistent with the strength of the flaps and other parts of the plane. Thus the pilot may set the usual manually operated control valve I3a for full ap application irrespective of his speed. If the speed should be so high that the stress on the flaps and connected parts might become excessive the hydraulic motor ISa and/or I8b or other fluid utilizing device will be reversed by such external overpowering force.v The liquid entrapped in line IIIJa and/or Ilb will then force the valve piston Ilaand/or IIlIb sulciently far to the right to permit the escape of liquid at IIla and/or I00b. This permits the now divider to rotate reversely so that the flaps will automatically assume a position where the stresses generated in the flaps and in the plane are not excessive. It will also be noted that the action of an overpowering force on only one wing flap will open both wing flaps to recede together.

When a drop in pressure occurs, the valve piston Ila will again move to the left under the action of spring Illa and restore the normal condition or assume such intermediate position as may be required by the forces acting upon the hydraulic motor ISa. The other valve piston IUIb will operate in the same manner under control of pressure in line I'Ib. It will be noted that the two throttling sections of the valves are arranged in series so that either one can eiect throttling, whereas, the two bleeder sections of the valves are arranged in parallel so that when either is open a reversal of the hydraulic motors and the flow divider can be effected.

Fig. 6 illustrates a form of the invention in. which both throttling and bleeding are used as in the case of Fig. 5, the throttling and bleeding being however effected by a single valve which is controlled by pilot valves which are responsive to the pressure in the respective outlet lines.

Referring to Fig. 6, the numerals II, I2, i3, l3nt, Isa', I4, I5, I6, I'Ia, I'Ib, Ica, I8b, Illa, Ich, I3', I3, 60, and 6I refer to parts substantially identical with parts of the same number appearing in Fig. 5. The numeral H5 indicates generally a body which may contain the now divider as well as the pressure control valves, although they may be arranged separately. I I5 indicates a cylindrical bore therein provided with annular enlargements III, IIS, and IIS. In said bore is located a piston I2!) having a central reduced portion IZI, a conical section |22 connecting said reduced portion with the lower full diameter portion ofthe'piston 'and' having a conical section |23 connecting the reduced portion with the upper full diameter section of the piston. The lower end of thepiston is shown as provided with a projection |24 to limit downward movement of the piston. A spring |25 tends to press the piston downwardly.

The conduit I4 is connected with the annular enlargement I II which ispnormally connected with the annular enlargement |I8 which is in communication with conduit I which is the inlet to .theflow divider. The annular enlargement IIS is always in communication with the return conduit |26. A passage |21 connects the space above the piston in which the spring is housed to the return conduit |26. f

The body is also formed with two cylindrical bores I30a and |30b, the upper ends of which are connected by passages I3Ia and I3Ib with the outlet lines I'Ia and I'Ib respectively. Said cylindrical bores are formed with annular enlargements I32a and |32b respectively, which enlargements areV connected to each other and through passage |33 to the conduit I5. Said bores also contain annular enlargements |34a and |3417 which are connected to each other and through passage |35 to the space below the valve piston 20.

, Said cylindrical bores |30a and |30b contain respectively valve pistons I36a and |3612 which are formed with central reduced portions. The pistons are normally held in the upper position shown by means of springs |3'|a and |3Ib, the bias Aof which may be varied by adjusting the adjustable spring abutment plugs I 38a and I 38h respectively. Any iluid accumulating under the pistons in the springl housings may be freed by connecting the two spaces to each other and through conduit |39 with the return conduitIZE. A passageV |40 having a restriction |4| therein connects the space below the valve pistonV |20 y with the return conduit |26. V

The operation of the device of Fig. 6 is as follows:

The conduit I4 is normally connectedto the conduit I5 through annular enlargements I I1 and IIB. However, if the pressure inone of the outlet lines, as for example outlet line IIa, should rise above the predetermined value for which the spring I3Ia has been set the pilot valve piston |36a will be moved downwardly. This admits iluid under pressure fromline I5 through passage |33, annular enlargements I32a and |34a, and conduit |35, tothe space below the valve piston 20, causing said piston to rise. In so doing, the conical section I 22 thereof approaches the limit of the annular enlargement Ill, thus throttling the flow of fluid from line I4 to line I5. If the valve piston should be moved still further, the conical section |23 of the valve piston |20 reaches the annular enlargement IIS and thereby permits iiuid from line I5 to be bled to the return line |26. This may occur'under the conditions described hereinabove with respect to the operation oi the form shown in Fig. 5. Upon the occurrence of a drop in pressure, the pilot valve piston |36a rises either to its upper position or to such an intermediate position as the conditions imposed upon hydraulic motor |8a may determine. As the pilot valve piston I 36a rises, the main valve piston |20 drops at a rate determined by the restriction |4I The six illustrative forms of the invention described abovehave the common characteristic that theywill prevent development of a pressure in any of A a plurality of outlet lines from a flow divider (and a corresponding excessive torque or" force in a uuid-utilizing device connected therewith), the pressure limiting being controlled by the pressure existing in any outlet line (irrespective of the pressure in the other outlet lines), and said pressure limiting means accomplishes its purpose without destroying the accuracy of now division.

The illustrative forms shown in Figs. 1, 2, 5, and 6 have in common the characteristic that if reverse flow should occur through overpoweringr of the fluid-utilizing device, by an externalV force escape of the fluid is provided for to prevent the development of excessive pressures, in the system and excessive stresses in the device operated thereby.

It will be noted that the constructions shown and described will serve admirably to accomplish the objects stated above. It is to be understood, however, that the constructions disclosed above are intended merely as illustrative of the invention and not as limiting, as various modifications therein may be made without departing from the invention as dened by a proper interpreta` tion of the claims which follow.

I claim: y 1. In a hydraulic system, a source of fluid under pressure, a iiow divider having an inlet conduit to which fluid is supplied from said source, a plurality of outlet conduits from said flow divider, and a plurality o! fluid-utilizing means one connected to each of said iluid outlets; the combination on a valve comprising means controlled by the pressure in any of said outlet conduits serving upon occurrence of a predetermined pressure in any outlet conduit to reduce the pressure in the inlet to the flow divider.

2. In a hydraulic system having a source of iluid `under pressure, a flow divider having an inlet conduit to which fluid is supplied from said source yand a, plurality of outlet conduits from said flow divider and a plurality of huid-utilizing means, the combination of a valve controlled by the pressure in any of said outlet conduits serving upon occurrence of a predetermined pressure in any outlet conduit to reduce the pressure in the inlet to the flow divider by bleeding fluid from said inlet conduit.

3. In a hydraulic system, asource of iluid under pressure, a flow divider having an inlet conduit to which uid is supplied from said source, a plurality of outlet conduits from said ilow divider, and means controlled by the pressure in any of said outlet conduits serving upon occurrence of a predetermined pressure in lany outlet conduit to reduce the pressure inthe inlet to the Aiow divider by throttling the conduit leading from va flow divider havingan inlet conduit to which iiuid is supplied from said source, and a plurality of outlet conduits from said iiow divider; said valve comprising means controlled by the pressure in any of said outlet conduits serving upon occurrence of a predetermined pressure in any outlet conduit to reduce the pressure in the inlet to the flow divider by throttling the conduit leading from the pressure source to the ow divider, and bleeding iluid from said inlet conduit upon the occurrence of a higher pressure in said outlet conduit, as by the action of an external force upon said fluid-utilizing means.

5. In a hydraulic system, a source of fluid under pressure, a flow divider having an inlet conduit to which iiuid is supplied from said source, a plurality of outlet conduits from said floW divider, and a plurality of valve means, one associated With each of said outlets, each controlled by the pressure in its associ-ated outlet conduit and each so constructed and arranged that upon occurrence of -a predetermined pressure in its associated outlet conduit it Will reduce the pressure in the inlet to the flow divider.

6. In a valve adapted for use in a hydraulic system having a source of fluid under p-ressure, a flow divider having an inlet conduit to which uid is supplied from said source, and a plurality of outlet conduits from said oW divider; said valve comprising a plurality of valve bodies, one associated with each of said outlets, each controlled by the pressure in its associated outlet conduit and each so constructed and arranged that upon occurrence of a predetermined precsure in its associated outlet conduit it Will reduce the pressure in the inlet to the flow divider by causing iluid to be bled from said inlet conduit.

7. In a hydraulic system, a source of iiuid under pressure, a owdivider having an inlet conduit to which fluid is supplied from said source, a plurality of outlet conduits from said llo-'W divider, and a plurality of valve means, one associated With each of said outlets, each controlled by the pressure in its associated outlet conduit and each so constructed and arranged that upon occurrence of a predetermined pressure in its associated outlet conduit it will reduce the pressure in the inlet to the flow divider by causing the conduit leading from the pressure source to the flow divider to be throttled.

8. Ina hydraulic system, a source of uid under pressure, a ow divider having an inlet conduit to Which fluid is supplied from said source, a plurality of outlet conduits from said flow divider, and a plurality of valve means, one associated with each of said outlets, each controlled by the pressure in its associated outlet conduit and each so constructed and arranged that upon occurrence of a predetermined pressure in its associated outlet conduit it will cause the pressure in the inlet to the flow divider to be reduced by throttling the conduit leading from the pressure source to the flow divider, and upon the occurrence of a higher pressure in its associated outlet conduit will bleed fluid from said inlet conduit.

9. Ina hydraulic system, a source of huid under pressure, -a ilow divider'having an inlet conduit to which iiuid is supplied from said source, a plurality of outlet conduits from said flow divider, a single pressure reducing valve and a plurality of pilot valves, one associated with each of said outlets, each controlled by the pressure in its associated outlet conduit and each so constructed and arranged that upon occurrence of a predetermined pressure in its associated outlet conduit it will actuate the said pressure reducing valve to reduce the pressure in the inlet to the :dow divider.

10. In a hydraulic system, a source of fluid under pressure, a flow divider having an inlet conduit to which uid is supplied from said source, a plurality of outlet conduits from said flow divider, a single pressure reducing valve and a plurality of pilot valves, one associated with each of said outlets, each controlled by the pressure in its associated outlet conduit and each so constructed and arranged that upon occurrence of a predetermined pressure in its associated outlet conduit it will actuate the said pressure reducing fifi fifa

lvalve to reduce the pressure in the. inlet :to the iioW divider, by bleeding fluid from said inlet conduit.

11. In a hydraulic system, a source of fluid under pressure, a low divider having an inlet conduit to which fluid is supplied from said source, a plurality of outlet conduits from said IloW divider, a single pressure reducing valve and a plurality of pilot valves, one associated with each of said outlets, each controlled by the pressure in its associated outlet conduit and each so constructed and arranged that upon occurrence of a predetermined pressure in its associated outlet conduit it will actuate the said pressure reducing valve to reduce the pressure in the inlet to the flow divider by throttling the conduit leading from the pressure source to the flow divider.

.12. In a hydraulic system of the type in which fluid under pressure is supplied to a flow divider having an inlet conduit and a plurality of outlet conduits, a single pressure reducing valve and a plurality of pilot valves, one associated with each of said outlets, each controlled by the pressure in its associated outlet conduit and each so constructed and arranged that upon occurrence oi a predetermined pressure in its associated outlet conduit it will actuate the said pressure reducing valve to reduce the pressure in the inlet to the iiow divider by throttling the conduit leading from the pressure source to the flow divider, and upon the occurrence of a higher pressure in its associated outlet conduit will bleed fluid from said inlet conduit.

13'. In a hydraulic system, a source of fluid under pressure, a flow divider having an inlet conduit to which fluid is supplied from said source, a plurality of outlet conduits from said flow divider, a plurality of valve pistons, one associated with each of said outlets, each of said pistons being slidably positioned in a bore formed with at least one port, spring means for normally holding said piston at one end of its stroke, said piston being so formed that said port is normally closed and that said port is opened when the piston is moved against the bias of said spring means, conduits leading from the port of each of said valves to the fluid supply conduit and to a discharge conduit, conduits leading from each of said outlet conduits to its associated valve bore and serving to transmit the pressure in its outlet to its associated valve piston to move it against the bias of its spring, whereby upon occurrenoe of a predetermined pressure in its associated outlet conduit the respective valve will reduce pressure in the inlet to the flow divider by bleeding fluid from said inlet conduit.

14. In a hydraulic system, a source of fluid under pressure, a iiow divider having an inlet conduit to which liuid is supplied from said source, a plurality of outlet conduits from said flow divider, a plurality of valve pistons, one associated with each of said outlets, each of said pistons being slidably positioned in a bore formed with at least one port, spring means for normally holding said piston at one end of its stroke, said piston being so formed that said port is normally open and that said port is gradually closed when the piston is moved against the bias of said spring means, conduits leading from the port of one of said valves to the fluid supply conduit and to the port of the other valve and from said other valve port to the inlet conduit, conduits leading from each of said outlet conduits to its associated valve bore and serving to transmit the pressure in its outlet to its associated valve piston to move it against the bias of its spring, whereby upon occurrence of a predetermined pressure in its associated outlet conduit the port of the respective valve will be closed and the pressure in the inlet to the fiow divider will be reduced by throttling the fluid supplied to said inlet conduit.

15. In a hydraulic system, a source of fluid under pressure, a flow divider having an inlet conduit to which fluid is supplied from said source, a plurality of outlet conduits from said flow divider, a plurality of valve pistons, one associated with each of said outlets, each of said pistons being slidably positioned in a bore formed with at least one port, spring means for normally holding said piston at one end of its stroke, said piston being so formed that said port is normally closed and that said port is gradually opened when the piston is moved against the bias of said spring means, conduits leading from the port of each of said valves to the fluid supply conduit and to a discharge conduit, conduits leading from each of'said outlet conduits to its associated valve bore and serving to transmit the pressure in its outlet to its associated valve piston to move it against the bias of its spring, whereby upon occurrence of a predetermined pressure in its, associated outlet conduit the port of the respective valve will be opened and the pressure in the inlet to the flow divider will be reduced by bleeding fluid from said inlet conduit.

16. In a hydraulic system having a source of fluid under pressure a ilow divider having an inlet conduit and a plurality of outlet conduits and a plurality of fluid-utilizing means one connected to each of said fluid outlets, the combination of valve means controlled by the pressure in either outlet conduit so constructed and arranged that upon occurrence of a predetermined pressure in one of the outlet conduits said valve means will reduce the pressure in the inlet to the flow divider by bleeding fluid from said inlet conduit.

17. In a hydraulic system having a source of fluid under pressure a flow divider having an inlet conduit and a plurality of outlet conduits and a plurality of fluid-utilizing means one connected to each of said fluid outlets, the combination of valve means controlled by the pressure in either outlet conduit so constructed and arranged that upon occurrence of a predetermined pressure in one of the outlet conduits said valve means will reduce the pressure in the inlet to the flow divider by throttling the conduit leading from the pressure source to the flow divider.

18. In a hydraulic system, a source of fluid under pressure, a flow divider having an inlet conduit to which fluid is supplied from said source, a plurality of outlet conduits from said flow divider, valve means controlled by the pressure in either outlet conduit so constructed and arranged that upon occurrence of a predetermined pressure in one of the outlet conduits said valve means Will reduce the pressure in the inlet to the flow divider by throttling the conduit leading from the pressure source to the flow divider, and upon the occurrence of a higher pressure will bleed fluid from said inlet conduit.

19. In a hydraulic system, a source of fluid under pressure, a iiow divider having an inlet conduit to which fluid is supplied from said source, a plurality of outlet conduits from said flow divider, a single spring-biased pressure reducing valve and a plurality of pilot valves, one associated with each of said outlets, each controlled by the pressure in its associated outlet conduit and each so constructed and arranged that upon occurrence of a predetermined pressure in its associated outlet conduit it will actuate the said pressure reducing valve against the bias of its spring to throttle the conduit leading from the pressure source to the flow divider, whereby the pressure in the inlet to the flow divider is reduced, and upon a further increase in pressure in said outlet to further actuate said pressure reducing valve to bleed fluid from said inlet conduit to permit reverse movement of said fluid-utilizing means.

LUKAS ZIMMERMANN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,968,700 Milotta s July 31, 1934 2,028,766 Ernst Jan. 28, 1936 2,214,817 Harrington Sept. 17, 1940 2,365,095 Miller Dec. 12, 1944 2,368,852 Lauck Feb. 6, 1945 2,374,630 Tucker Apr. 24, 1945 

